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Evidence for Evolution

Evidence for Evolution. Biology 9. EVIDENCE FOR EVOLUTION. What is the evidence that all species on earth are related to each other and share common ancestors? Overview: 4 Major Types of Evidence: Homologous Structures Embryos Gene Sequences Fossils. 1. HOMOLOGOUS STRUCTURES –

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Evidence for Evolution

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  1. Evidence for Evolution Biology 9

  2. EVIDENCE FOR EVOLUTION What is the evidence that all species on earth are related to each other and share common ancestors? Overview: 4 Major Types of Evidence: • Homologous Structures • Embryos • Gene Sequences • Fossils

  3. 1. HOMOLOGOUS STRUCTURES – Similar body parts or bone structures due to sharing a common ancestor that had those structures • Don’t necessarily have the same function now, but did in the common ancestor • Ex: human arm, cat leg, whale flipper, bat wing all have same bones

  4. Homologous Structures, continued: Vestigial Traits - • Don’t have a function now, but suggest that they descended from an ancestor that did use them. • Examples: • human tailbone, human goose bumps, ostrich wingsEx: human tail bone, human goose www.toptenz.net animal.nationalgeographic.com

  5. Don’t confuse Homologous Structures with Analogous Structures Analogous Structures - structures that have the same function but NOT the same skeletal structure • This suggests these organisms did NOT descend from a common ancestor with that trait Ex: insect wing and bird wing Bird wing Insect wing bio.miami.edu

  6. 2. Embryos Similar characteristics appearing during specific embryonic/ developmental stages of development • Example: Fish, reptile, bird, and human embryos all have gill slits and a tail (but some lose these features before birth)

  7. 3. Gene Sequences Similarities between DNA or amino acid sequences for different organisms • Closer the similarities = Closer relationships

  8. 4. FOSSILS Fossils show… • show species that are now extinct • show transitions to new body forms • Example: Tiktaalik (lived 375 million years ago) • fish with legs and (maybe) primitive lungs… • earliest amphibian? • Objectives for Class: • Describe how fossils are used as evidence for evolution and give one example that illustrates this. Artist Rendering Fossil

  9. FOSSILS, cont. • Example: Archaeopteryx (lived 150 million years ago) • earliest bird… but has many dinosaur features • Objectives for Class: • Describe how fossils are used as evidence for evolution and give one example that illustrates this. www.ansp.org

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